Enhanced efficiency in flexible dye-sensitized solar cells by a novel bilayer photoanode made of carbon nanotubes incorporated TiO2 nanorods and branched TiO2 nanotubes

The branched TiO 2 nanotubes (BTNTs) were synthesized by a combined method of electrospinning, hydrothermal treatment , calcination , and ultrasonic treatment . Various morphologies of BTNTs were obtained by adjusting the hydrothermal temperature or time, and this yielded a morphologically-controllable BTNTs geometry. The CNTs incorporated TiO 2 nanorods (CTNRs) were fabricated via a combined method. The novel bilayer photoanodic film made of the CTNRs as an underlayer and the BTNTs as a light-scattering overlayer was fabricated for flexible dye-sensitized solar cells (FDSSCs). With addition of the BTNTs, the conversion efficiency of FDSSCs was greatly enhanced due to the improved light-scattering, the increased dye loading, and the more effective electron collection. The highest conversion efficiency of 4.18% was achieved with the 150   °C hydrothermal treatment for 30   min, which is nearly twice that of the FDSSCs using single-layer CTNRs film.